Dam fed unrollable media filter subsequently folded along its length and rewound

ABSTRACT

According to a waste water treatment method and apparatus of the present invention, a permeable sheet  3  is fed into a treatment tank  2  in which a stream is formed. The waste water, which flows downstream, is caused to pass through the permeable sheet  3 , while the permeable sheet  3  travels in the treatment tank  2  so as to traverse the surface of the waste water on a downstream side in the flowing direction of the waste water. Therefore, not only the sludge in the waste water but also the oily substances floating in the waste water can be collected and removed because they cling to the permeable sheet  3  and are gathered by it. As a result, a waste water treatment tank  2  and the like can be maintained in a usable state for a long time. In addition, there can be obtained a treated water to which microbial treatment can be applied.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Divisional of application Ser. No. 09/306,598,filed on May 6, 1999, which is currently “allowed” and pending “issue.”

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a waste water treatment method andapparatus for collecting sludge, oily substances, scum, and so on whichexist in waste water, float and precipitate therein and for reducing thevolume thereof by dehydrating them.

2. Description of the Related Art

Conventionally, waste water, which was discharged from kitchens, meatand marine product processing factories, oil manufacturing factories,oil and fat processing factories, repair shops, gas stations, and thelike, included a large amount of wastes which contained animal oils andfats, vegetable oils and mineral oils, and wastes containing animal andvegetable oily substances which were made when various materials wereprocessed.

Since these wastes must be previously removed from the waste water whenthe waste water is treated, they were conventionally separated andremoved with nets, screen meshes and the like. However, when the wastewater contains oily substances, they float in the waste water or on thesurface thereof as grease-like lumps containing water and sludge or asscum-like lumps containing bubbles.

When the waste water is to be purified, it is an important theme tosubject the waste water to biological treatment to permit a prescribedquantity of microorganisms to live in the waste water.

Microorganisms in water have a self-purifying capability. When, however,the amount of oxygen supplied into the water is smaller than the amountof oxygen consumed by them, aerobic microorganisms, which live by takingoxygen, will die because the amount of oxygen dissolved in water isreduced. When no oxygen exist in the water, anaerobic microorganisms,which take oxygen contained in organic matters, will breed and reduceand decompose the organic matters.

The biological treatment is classified into an aerobic treatment and ananaerobic treatment: in the aerobic treatment, oxygen contained in airis sufficiently supplied to polluted water by aeration and the like sothat dirt is decomposed and purified; whereas, in the anaerobictreatment, air is prevented from being in contact with polluted water sothat anaerobic organisms breed in the area where no oxygen exists anddecompose and purify the dirt.

However, since the waste water from kitchens and the like contains alarge amount of suspended oily substances, the waste water has a problemthat oil sludge clings to a fluidized bed, that is, to the surfaces ofcarriers onto which microorganisms cling and chokes the microorganismsclinging onto the carriers when the biological treatment is performed.

Since the waste water containing the oily substances clogs nets, screenmeshes and the like, the oily substances cannot be separated andremoved. The animal oils and fats contained in waste water dischargedfrom kitchens and the like are not solidified while they are at a hightemperature. However, since they are solidified when cooled in suchplaces as a raw water tank for treating waste water, a cesspool locatedat some midway point and a watercourse, the flow of the waste water isobstructed by the solidified animal oils and fats and cannot be treatedwell.

To remove scum and the like clinging to the tank and the like, there wasconventionally employed a method of heating the portions of them whichare liable to precipitate by steam or hot water piping. However, thescum and the like which contain sludge and residues, become creamy orsometimes contain bubbles have a problem that they cannot be removedeven if they are heated as well as they are removed in only a limitedamount even if a worker remove them with a rod or a ladle. Thus, therearises a problem that raw water tanks for treating waste water,cesspools located at some midway point and the like are made unusable.

SUMMARY OF THE INVENTION

To solve the above problems, a first object of the present invention isto provide a waste water treatment method and apparatus capable ofobtaining treated water which can be subjected to a microbial treatmentby at least collecting and removing oily substances floating in wastewater.

A second object of the present invention is to provide a waste watertreatment method and apparatus capable of maintaining a waste watertreatment tank for storing and treating waste water and the like in ausable state for a long time by collecting and removing not only sludgeprecipitating in the waste water but also oily substances floating inthe waste water.

The waste water treatment method of the present invention ischaracterized by comprising the steps of supplying waste watercontaining oily substances into a treatment tank and storing the wastewater in the treatment tank; forming a stream to the waste water forcausing the waste water to flow out of the treatment tank; feeding apermeable sheet into the treatment tank; causing the waste water, whichflows downstream, to pass through the permeable sheet, while thepermeable sheet travels in the treatment tank so as to traverse thesurface of the waste water on a downstream side; and collecting thewaste water having passed through the permeable sheet by causingprecipitates and floating substances to cling onto the permeable sheetand gathering them by the permeable sheet.

According the above distinctive feature, the permeable sheet is fed intothe treatment tank in which the stream is formed. The waste water, whichflows downstream, is caused to pass through the permeable sheet, whilethe permeable sheet travels in the treatment tank toward the outside soas to traverse the surface of the waste water on the downstream side inthe flowing direction of the waste water. Therefore, not only the sludgein the waste water but also the oily substances floating in the wastewater can be collected and removed because they cling to the permeablesheet and are gathered by it. As a result, a waste water treatment tankand the like can be maintained in a usable state for a long time.

According to the waste water treatment method of the present invention,it is preferable that the permeable sheet is continuously orintermittently fed and collected.

With this arrangement, since the fresh surface of the permeable sheet isalways fed, the clogging of the permeable sheet can be prevented and theclinging property of it can be improved.

According to the waste water treatment method of the present invention,it is preferable that the permeable sheet is moved while it is inclinedobliquely upward with respect to the direction in which the waste waterflows.

With this arrangement, since the area of the permeable sheet, onto whichthe substances floating on the surface of the waste water flowingdownstream cling, is increased by the inclination of the permeablesheet, the filtrating effect of the permeable sheet can be improved.

According to the waste water treatment method of the present invention,it is preferable that the permeable sheet is pressed after precipitatesand floating substances cling onto the permeable sheet.

With this operation, since the water contained in the permeable sheet isremoved by pressing the permeable sheet, the weight of the permeablesheet can be reduced as well as the permeable sheet can be easilydestroyed by fire in the next process.

According to the waste water treatment method of the present invention,it is preferable that the permeable sheet is pressed by a press meansafter it is folded to two strip-shaped sections by a guide means whileit is moved.

With this arrangement, since the permeable sheet is folded to the twosections, the fluid oily substances, sludge and the like which cling tothe permeable sheet can be continuously pressed without removing fromthe permeable sheet.

According to the waste water treatment method of the present invention,it is preferable that the permeable sheet having been pressed isdestroyed by fire in the state it is wound to a roll shape or in thestate as it is as a strip shape.

With this operation, since the permeable sheet is wound to the rollshape or formed to the strip shape, it can be made compact and easilytransported. Further, the permeable sheet can be sanitarily disposed ofbecause it is destroyed by fire so that germs and the like die out.

A waste water treatment apparatus of the present invention ischaracterized by comprising a treatment tank in which waste watercontaining oily substances is stored so as to form a stream; a permeablesheet continuously or intermittently fed to the vicinity of the bottomof the treatment tank; and a permeable sheet drive unit for collectingthe permeable sheet so that it traverses at least the surface of thewaste water with respect to the stream of the waste water on adownstream side, wherein the waste water flowing downward is caused topass through the permeable sheet to thereby obtain purified water.

According to the above distinctive feature, the permeable sheet is fedinto the treatment tank in which the stream is formed by driving thepermeable sheet drive unit. The waste water, which flows downstream, iscaused to pass through the permeable sheet, while the permeable sheettravels in the treatment tank toward the outside so as to traverse thesurface of the waste water on the downstream side in the flowingdirection of the waste water. Therefore, not only the sludge in thewaste water but also the oily substances floating in the waste water canbe collected and removed because they cling to the permeable sheet andare gathered by it. As a result, the waste water treatment tank and thelike can be maintained in a usable state for a long time.

A waste water treatment apparatus of the present invention ischaracterized by comprising a waste water storing tank for storing wastewater containing oily substances and supplied thereinto; a waste watertreatment tank for storing the waste water having been treated; a damwith a prescribed width formed to the upper end edge of the waste waterstoring tank on a downstream side for causing at least the upper surfaceof the waste water to flow out of the dam; and a strip-shaped permeablesheet fed from just below the dam so as to traverse obliquely upward thewaste water flowing out of the dam in the flowing direction of the wastewater, wherein the waste water having been treated through the permeablesheet is stored in the waste water treatment tank.

According to the above distinctive feature, since the waste water, whosestream is formed in the treatment tank, is caused to pass through thepermeable sheet which is continuously fed, at least the oily substancesfloating in the waste water in the treatment tank can be collected andremoved because they cling to the permeable sheet and are gathered byit. As a result, a treated water to which microbial treatment can beapplied can be obtained.

According to the waste water treatment apparatus of the presentinvention, it is preferable that the permeable sheet is stretchedthrough a guide means so as to traverse obliquely upward the surface ofthe waste water on the downstream side of the waste water treatmenttank, the extended portion of the permeable sheet is folded and pressedby a press means while the extended portion is moved and the pressed andfolded permeable sheet is wound by a winding means in a stretched state.

With this arrangement, since the water contained in the permeable sheetis removed by pressing the permeable sheet, the weight of the permeablesheet can be reduced as well as the permeable sheet can be easilydestroyed by fire in the next process.

According to the waste water treatment apparatus of the presentinvention, it is preferable that the permeable sheet is composed of anonwoven fabric cloth or a waterproof converted paper.

With this arrangement, since the flowing waste water is filtered throughthe permeable sheet, even if the permeable sheet is dipped into thetreatment tank, the strength of the permeable sheet can be maintainedfor a long time.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an overall perspective view showing the state that a permeablesheet which is used to a waste water treatment apparatus as a firstembodiment of the present invention is laid in a treatment tank;

FIG. 2 is a side elevational view describing the waste water treatmentapparatus as a whole;

FIG. 3 describes a test method performed by a biological treatment testdevice before and after waste water is treated;

FIG. 4 shows a graph illustrating the time series change of a biologicaltreatment to a COD value before and after waste water is treated;

FIG. 5 shows a graph illustrating the time series change of a biologicaltreatment to NH₄—N and chromaticity before and after waste water istreated; and

FIG. 6 is a perspective view of the waste water treatment apparatus as asecond embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Embodiments of the present invention will be described based on thedrawings. FIG. 1 is an overall perspective view showing the state that apermeable sheet which is used to a waste water treatment apparatus islaid in a treatment tank and FIG. 2 is a side elevational viewdescribing the waste water treatment apparatus as a whole.

First, a first embodiment of the waste water treatment apparatus of thepresent invention will be described. As shown in FIG. 1 and FIG. 2,numeral 1 denotes a waste water treatment apparatus which is essentiallycomposed of a treatment tank 2 for storing a dirty waste water 4 whichis discharged from the kitchens and the like of restaurants, hotels, andother eating houses to a waste water storage tank 6, temporarily storedtherein and supplied therefrom; a permeable sheet 3, which iscontinuously or intermittently fed into the waste water stored in thetreatment tank 2 so as to form a stream, for removing oily scum floatingin the waste water and sludge and the like precipitating in the wastewater 4 as well as filtrating the waste water 4, a treated water storagetank 8 for storing a treated waste water 5 which is filtered through thepermeable sheet 3 and supplied by a pump 7.

More specifically, a prescribed stream is formed in the treatment tank 2in such a manner that the waste water 4 containing oily substances issupplied from the waste water storage tank 6 into the treatment tank 2and then supplied from the treatment tank 2 into the treated waterstorage tank 8 by the pump 7 in a prescribed quantity.

The waste water 4 to be treated gets muddy to white and containscountless fine fiber-like suspended matters floating therein and oilyscum (grease-like) floating matters composed of soft and hard white fatscontaining water and having a size of about 2-10 mm.

In this case, the waste water 4 which flows into the treatment tank 2having a height H has a depth h up to a water surface F which ismaintained to a constant level at all times because the flow rate of thewaste water 4 flowing out of the treatment tank 2 is regulated by thepump 7.

The permeable sheet 3 used in the waste water treatment apparatus 1comprises a nonwoven fabric cloth or a waterproof converted paper. Morespecifically, it is preferable that the permeable sheet 3 compriseshighly hydrophilic fibers used for paper pulp or fibers composed of ahydrophilic polymer containing a hydrophilic group such as polyester,polyvinylalcohol, etc. and fibers composed of a hydrophobic polymercompound such as polypropylene, polyethylene, etc.

Since the permeable sheet 3 mainly comprises the waterproof convertedpaper such as a recycled paper or the like and the strength of thepermeable sheet 3 can be obtained by the fibers such as polyethylene,polyester, etc., even if the permeable sheet 3 is dipped into the wastewater in the treatment tank, the strength of the permeable sheet 3 canbe maintained for a long time. In addition, floating oily substances andthe like can be collected by preferably filtering the flowing-out wastewater while balancing a lipophilic property and a hydrophilic property.

The permeable sheet 3 arranged as described above is formed to a stripshape and wound to a roll shape. A roll member 3 a is rotatablysupported at an end of the treatment tank 2 on an upstream side. Thepermeable sheet 3 is bent and guided from above the opening of thetreatment tank 2 at an end thereof by horizontally-supported guiderollers 9 a, 9 b, 9 c and laid above the bottom of the treatment tank 2.Further, the permeable sheet 3 is fed upward from the guide roller 9 cso as to traverse the surface F of the waste water obliquely upward withrespect to the stream of the waste water 4 on a downstream side, bentapproximately horizontally in a longitudinal direction by a guide roller9 d disposed at an upper position, and the lower surface of thehorizontally extended portion of the permeable sheet 3 is supported by aguide roller 9 e.

A pair of squeeze rollers 12 as press members are vertically supportedin close proximity to and parallel with each other at the position wherethe guide roller 9 e is supported. The edges of the upper surface onboth the sides of the permeable sheet 3, which has been flatly extendedand laid above the bottom of the treatment tank 2, are gradually bent ina width direction from the position where the permeable sheet 3 haspassed through the guide roller 9 d, and the extended portion of thepermeable sheet 3 is folded to two sections by the squeeze rollers 12and both the sides of the permeable sheet 3 are squeezed and pressed bythe squeeze rollers 12. The permeable sheet 3 having passed through thesqueeze rollers 12 is wound to a roll shape in a longitudinal directionin a stretched state by a winding member 3 b which is rotated by a notshown drive unit.

A pair of vertical rollers 10 a and 10 b and a pair of vertical rollers11 a, 11 b are vertically supported between the guide roller 9 ddisposed at the upper position and the squeeze rollers 12 to graduallynarrow the width of the permeable sheet 3. The permeable sheet 3 isregulated in the width direction thereof by the vertical rollers 10 a,10 b and 11 a, 11 b so that the bent heights of both the side edges ofthe permeable sheet 3 are not abruptly increased and both the side edgesare gradually raised from the inclined surface of the permeable sheet 3to obtain a flat surface in a prescribed area. With this arrangement,the oily substances and the like clinging onto the upper surface of thepermeable sheet 3 are kept from spilling.

According to the waste water treatment apparatus arranged as describedabove, first, the roll member 3 a around which the strip-shapedpermeable sheet 3 is wound is rotatably supported at the one end of thetreatment tank 2, the permeable sheet 3 drawn from the roll member 3 ais fed obliquely upward through a portion of the bottom of the treatmenttank 2 and gradually squeezed while both the end edges of the extendedportion of the permeable sheet 3 are folded upward in the widthdirection thereof, both the sides of the permeable sheet 3 folded to thetwo sections are pressed by the pair of squeeze rollers 12 andsubsequently the permeable sheet 3 is wound to the roll shape by thewinding member 3 b so that it is laid in the stretched state as shown inFIG. 1 and FIG. 2.

In this state, the waste water 4 containing oily substances, which isdischarged from a not shown kitchen or the like, is discharged from thewaste water storage tank 6 onto the permeable sheet 3 laid above thebottom of the treatment tank 2 in a prescribed quantity and stored inthe treatment tank 2 until the depth of the surface of the waste water 4is made to h. At the time, the waste water is caused to flow into thetreated water storage tank 8 by starting the pump 7 to thereby form thestream in the treatment tank 2.

The winding member 3 b which is rotated by a worker or power permits thepermeable sheet 3 to move in the longitudinal direction while beingpulled.

The waste water 4, which contains the oily substances and iscontinuously supplied into the treatment tank 2, is stored therein aswell as a slow stream is formed to the waste water 4. When oil sludgeand the like cling onto the upper surface of the permeable sheet 3 aftera while in the process that the waste water 4 is caused to pass throughthe obliquely stretched permeable sheet 3 by the stream, the level ofthe treated waste water 5 having passed through the permeable sheet 3 issomewhat lowered as compared with the initial level of it.

When the permeable sheet 3 is moved by a prescribed length in thelongitudinal direction by rotating the winding member 3 b little bylittle, the waste water 4 passes through the surface of the inclinedpermeable sheet 3 in the process it is moved, whereby the oilysubstances and the like floating in the waste water 4 are caused tocling onto the upper surface of the permeable sheet 3.

Next, the treated waste water 5 having been treated by passing throughthe permeable sheet 3 is supplied into the treated water storage tank 8by the pump 7 and stored therein.

With this operation, not only the sludge precipitating in the wastewater 4 but also the oily substances floating in the waste water 4 arecollected and removed by clinging onto the permeable sheet 3 and beinggathered by it in such a manner that the permeable sheet 3 is fed to thebottom of the treatment tank 2 from the upstream side of the treatmenttank 2; while the permeable sheet 3 passes through a portion of thebottom of the treatment tank 2, it is continuously or intermittently fedtoward the outside so as to traverse the surface of the waste water onthe downstream side thereof obliquely upward in the flowing direction ofthe waste water so that the waste water 4 flowing downstream passesthrough the permeable sheet 3. As a result, the treatment tank 2 and thelike can be maintained in a usable state for a long time.

Next, a second embodiment of the waste water treatment apparatus of thepresent invention will be described. FIG. 6 is a perspective view of thewaste water treatment apparatus as the second embodiment of the presentinvention. The same numerals as used for the above components are usedto denote the same components and overlapping description will beomitted.

The second embodiment is different from the first embodiment in that adischarging dam is formed on an end of a treatment tank and only theoily substances floating in waste water is collected in such a processthat the waste water which has flown into the treatment tank and hasbeen stored in it is caused to pass through a permeable sheet when itflows out of the treatment tank.

That is, numeral 14 denotes a waste water treatment apparatus which iscomposed of two treatment tanks, that is, a waste water storing tank 19into which waste water 4 containing oily substances flows and is storedtherein and a waste water treatment tank 21 for storing the waste waterhaving been treated. A dam 20 with a prescribed width, from which atleast the upper portion of the waste water 4 can flow out, is formed tothe upper end edge of the waste water storing tank 19 on a downstreamside. A strip-shaped permeable sheet 3 is continuously or intermittentlyfed from just below the dam 20 so as to traverse obliquely upward thewaste water 4 flowing out of the dam 20 in the flowing direction of thewaste water 4. A treated waste water 5 having been treated through thepermeable sheet 3 is stored in the waste water treatment tank 21.

More specifically, the dam 20 projecting from the upper end edge of thewaste water storing tank 19 has a width near to the width of the wastewater storing tank 19 and a shallow depth. A roll member 3 a aroundwhich the strip-shaped permeable sheet 3 is wound is rotatably andhorizontally supported just below the dam 20.

The permeable sheet 3 drawn out from the roll member 3 a is squeezed bya horizontally supported guide roller 15, a pair of guide rollers 16 aand 16 b, and a pair of guide rollers 17 a and 17 b. The pair of guiderollers 16 a and 16 b are supported in an inclined state for supportingthe extended portion of the permeable sheet 3 stretched obliquely upwardfrom the guide roller 15 from both the sides thereof in the state thatthe extended portion of the permeable sheet 3 is bent to a V-shape withthe upper surface thereof facing inward in the inclined state. The pairof guide rollers 17 a and 17 b are supported in the state that they areinclined more than the pair of guide rollers 16 a and 16 b. Thereafter,the extended portion of the permeable sheet 3 is pressed by a pair ofsqueeze rollers 18 which are disposed in close proximity to each otherand wound to a roll state by a winding member 3 b rotated by, forexample, a not shown drive unit in the state that it is stretched in alongitudinal direction.

The permeable sheet 3 drawn out from the roll member 3 a is stretchobliquely upward from the guide roller 15. However, the permeable sheet3 may be stretched so as to be inclined in an opposite direction (in adescending direction) by another guide roller disposed forward of theguide roller 15. At the time, even if what clings onto the permeablesheet 3 is a fluid substance, it can be reliably captured withoutflowing down along the permeable sheet 3.

In the waste water treatment apparatus 14 arranged as described above,the waste water 4 which contains oily substances and the like and isdischarged from a not shown kitchen or the like is discharged from, forexample, a waste water storage tank 6 into the waste water storing tank19 in a prescribed quantity. When the level of the waste water is raisedand the upper portion of the waste water which has passed through thedam 20 is caused to flows out, the waste water is filtered when itpasses through the permeable sheet 3 stretched in the inclined state,the oily substances floating in the waste water 4 cling onto thepermeable sheet 3, and the treated waste water 5 having passed throughthe permeable sheet 3 is caused to flow out of a discharge port 22 intothe waste water treatment tank 21 by a not shown pump and storedtherein.

The treated waste water 5 stored in the waste water treatment tank 21does not disturb the execution of a microbial treatment because it isfiltered through the permeable sheet 3, which will be described later indetail.

With the above arrangement, when the waste water treatment tank 21 shownin FIG. 6 is used as a portion of a grease pit for waste watercontaining a large quantity of oily substances or as a portion of anoily water separator, it can easily collect and dehydrate the oilysubstances.

When the waste water treatment tank 21 is equipped with anaggregating/floating treatment apparatus for waste water, even floatingscum can be simply and easily collected and dehydrated, although it isdifficult to treat the floating scum by an ordinary treatment.

Next, a waste water treatment method of the present invention will bedescribed. FIG. 3 describes a test method performed by a biologicaltreatment test device before and after waste water is treated, FIG. 4shows a graph illustrating the time series change of the biologicaltreatment to a COD value before and after waste water is treated, andFIG. 5 shows a graph illustrating the time series change of thebiological treatment to NH₄—N and chromaticity before and after wastewater is treated.

The waste water treatment method of the present invention treats wastewater using the waste water treatment apparatus 1, which is shown inFIG. 1 and FIG. 2 and embodies the waste water treatment method of thepresent invention.

That is, according to the waste water treatment method, the waste water4 containing the oily substances flows into the treatment tank 2 and isstored therein as well as a stream is formed by causing the waste water4 to flow out in a prescribed quantity; the permeable sheet 3 is fed tothe bottom of the treatment tank 2 from the one end of the treatmenttank 2 on the upstream side thereof and then fed toward the outside ofthe treatment tank 2 so as to traverse the surface F of the waste wateron the downstream side thereof obliquely upward in the flowing directionof the waste water while the permeable sheet 3 passes through a portionof the bottom of the treatment tank 2; the permeable sheet 3 gathersprecipitates such as cooked food material waste, residues removed fromtableware being washed, and the like, and floating substances such asanimal and vegetable fats which float in a scum state by causing them tocling to the permeable sheet 3 when it passes through the waste water 4flowing downstream; the treated waste water 5 having passed through thepermeable sheet 3 is collected; and the permeable sheet 3 is dehydratedby being folded and pressed.

Table 1 shows the quality of the waste water 4 at a portion B before itwas treated through the treatment tank 2 shown in FIG. 2 and the qualityof the treated waste water 5 after it was treated through the permeablesheet 3.

Table 1

According to Table 1, the waste water having been treated is not greatlydifferent from the waste water before it is treated as to NH₄—N (ammonianitrogen) and chromaticity. However, the values of a chemical oxygenconsumption (COD), a suspended substance (SS) and a N-hexane extract ofthe waste water 4 before it is treated are greatly reduced as comparedwith those of the treated waste water 5.

This exhibits that the oily substances have been sufficiently removed,and thus it is expected that the execution of the biological treatmentis not disturbed by the sludge which includes the oily substances andclings onto the surfaces of carriers to which microorganisms are fixed.

Next, the changes of the COD, the NH₄—N and the chromaticity of thewaste waters before and after they were treated were observed in timeseries using a test device 24 shown in FIG. 3.

In the test device 24, a volume of 5 liters of the waste water before orafter it was treated was accommodated in a transparent cylinder 25having a height H of 72 cm so that the depth h of the waste water wasmade to 62 cm, and bubbles 29 were generated by charging air from asmall blower 26 into the waste water through an air diffusing air stone27 disposed on the bottom of the cylinder 25.

Cylindrical plastic pieces (diameter: 10 mm, length: 10 mm) made byTsutsunaka Plastic Co. Ltd. were used in the quantity of 750 millilitersto the 5 liters of the waste water (volume ratio: 15%) as fluidized bedfixing carriers 28.

As fixing carriers for fixing microorganisms for purifying waste water,the fixing carriers which had been used for the treatment of the wastewater and onto which microorganisms had clung were used after themicroorganisms were previously domesticated in the waste water from akitchen for one week.

As a result, as shown in the graph of FIG. 4, although the COD value ofthe waste water shown by a dotted line was reduced from 178 ppm to 78ppm in 48 hours before it was treated, it was not changed thereafter.

Since the nutrients required by the microorganisms in the waste waterfrom a kitchen are not balanced as compared with the nutrients requiredby the microorganisms in a combined treatment tank, it is conceived thatthe limit of the COD value is about 30 ppm which is by no means obtainedin the waste water even in time series before it is treated. However,the COD value of 30 ppm can be obtained in 43.5 hours in the waste waterafter it is treated as shown by the solid line of FIG. 4.

Further, as shown in the graph of FIG. 5, the values of the NH₄—N andthe chromaticity were greatly reduced in time series.

As described above, the same effect as that obtained by the above wastewater treatment apparatus can be also obtained by the embodiment of thewaste water treatment method and the description of it is omitted herebecause it is overlapped.

Since the permeable sheet 3 is continuously or intermittently fed andcollected, the fresh surface of it is always supplied, whereby theclogging of the permeable sheet 3 is prevented and the clinging propertythereof is improved.

Since the permeable sheet 3 is disposed obliquely upward with respect tothe flowing direction of the waste water, the area of the permeablesheet, onto which the substances floating on the surface of the wastewater which flows downward cling, is increased by the inclination of thepermeable sheet 3.

Further, since permeable sheet 3 is pressed, the water contained in theoily substances clinging to the permeable sheet 3 and gathered by it isremoved in the process in which the permeable sheet 3 is pressed. Thus,the oily substances can be easily destroyed by fire. In addition, sincethe permeable sheet 3 is wound to the roll shape or formed to the stripshape, it is light in weight and compact and can be easily transported.

While the embodiments of the present invention have been described abovewith reference to the drawings, the specific arrangement of the presentinvention is by no means limited to the above embodiments and it goeswithout saying that various modifications and additions made within therange which does not depart from the gist of the present invention canbe included in the invention.

The present invention will achieve the following effects.

(a) According to a first aspect of the present invention, the permeablesheet is fed into the treatment tank in which the stream is formed. Thewaste water, which flows downstream, is caused to pass through thepermeable sheet, while the permeable sheet travels in the treatment tanktoward the outside so as to traverse the surface of the waste water onthe downstream side in the flowing direction of the waste water.Therefore, not only the sludge in the waste water but also the oilysubstances floating in the waste water can be collected and removedbecause they cling to the permeable sheet and are gathered by it. As aresult, a waste water treatment tank and the like can be maintained in ausable state for a long time.

(b) According to a second aspect of the present invention, since thefresh surface of the permeable sheet is always fed, the clogging of thepermeable sheet can be prevented and the clinging property of it can beimproved.

(c) According to a third aspect of the present invention, since the areaof the permeable sheet, onto which the substances floating on thesurface of the waste water flowing downstream cling, is increased by theinclination of the permeable sheet, the filtrating effect of thepermeable sheet can be improved.

(d) According to a fourth aspect of the present invention, since thewater contained in the permeable sheet is removed by pressing thepermeable sheet, the weight of the permeable sheet can be reduced aswell as the permeable sheet can be easily destroyed by fire in the nextprocess.

(e) According to a fifth aspect of the present invention, since thepermeable sheet is folded to the two sections, the fluid oilysubstances, sludge and the like which cling to the permeable sheet canbe continuously pressed without removing from the permeable sheet.

(f) According to a sixth aspect of the present invention, since thepermeable sheet is wound to the roll shape or formed to the strip shape,it can be made compact and easily transported. Further, the permeablesheet can be sanitarily disposed of because it is destroyed by fire sothat germs and the like die out.

(g) According to a seventh aspect of the present invention, thepermeable sheet is fed into the treatment tank in which the stream isformed by driving the permeable sheet drive unit. The waste water, whichflows downstream, is caused to pass through the permeable sheet, whilethe permeable sheet travels in the treatment tank toward the outside soas to traverse the surface of the waste water on the downstream side inthe flowing direction of the waste water. Therefore, not only the sludgein the waste water but also the oily substances floating in the wastewater can be collected and removed because they cling to the permeablesheet and are gathered by it. As a result, a waste water treatment tankand the like can be maintained in a usable state for a long time.

(h) According to an eighth aspect of the present invention, since thewaste water, whose stream is formed in the treatment tank, is caused topass through the permeable sheet which is continuously fed, at least theoily substances floating in the waste water in the treatment tank can becollected and removed because they cling to the permeable sheet and aregathered by it. As a result, there can be obtained a treated water towhich microbial treatment can be applied.

(i) According to a ninth aspect of the present invention, since thewater contained in the permeable sheet is removed by pressing thepermeable sheet, the weight of the permeable sheet can be reduced aswell as the permeable sheet can be easily destroyed by fire in the nextprocess.

(j) According to a tenth aspect of the present invention, since theflowing waste water is filtered through the permeable sheet, even if thepermeable sheet is dipped into the treatment tank, the strength of thepermeable sheet can be maintained for a long time.

TABLE 1 Type Volume COD NH₄—N Chromatisity SS N-hexane extract Portion BWaste water 0.5 l 178 ppm 1.6 ppm 74 630 ppm 491 ppm from kitchenPortion C Treated water 0.7 l 120 ppm 1.7 ppm 64 216 ppm 23 ppm

What is claimed is:
 1. A waste water treatment apparatus, comprising: awaste water storage tank for storing waste water containing oilysubstances and supplied thereinto; a waste water treatment tank forstoring the waste water having been treated; a dam with a prescribedwidth formed to the upper end edge of said waste water storage tank on adownstream side for causing at least the upper surface of the wastewater to flow out of said dam; a strip-shaped permeable sheet fed from aroll just below said dam so as to traverse obliquely upward the wastewater flowing out of said dam in the flowing direction of the wastewater; a plurality of guide rollers causing said strip-shaped permeablesheet to be folded along its length; and a winding member to wind theresultant folded sheet into a roll; wherein the waste water having beentreated by passing through said permeable sheet is stored in said wastewater treatment tank.
 2. A waste water treatment apparatus according toclaim 1 and including a drive for continuously or intermittently feedingand collecting the permeable sheet.
 3. A waste water treatment apparatusaccording to claim 2, wherein the permeable sheet is inclined obliquelyupward with respect to the direction in which the waste water flows. 4.A waste water treatment apparatus according to claim 1, and comprisingpress members for pressing the permeable sheet after precipitates andfloating substances cling onto the permeable sheet.
 5. A waste watertreatment method according to claim 1, and further comprising pressmembers for pressing the permeable sheet after it is folded to twostrip-shaped sections by said guide members.
 6. A waste water treatmentapparatus according to claim 1, wherein said permeable sheet isstretched through a guide means so as to traverse obliquely upward thesurface of the waste water on the downstream side of said treatmenttank, the extended portion of said permeable sheet is folded and pressedby press members while the extended portion is moved and the pressed andfolded permeable sheet is would by a winding member in a stretchedstate.
 7. A waste water treatment apparatus according to claim 6,wherein said permeable sheet comprises a nonwoven fabric cloth or awaterproof converted paper.
 8. A waste water treatment apparatusaccording to claim 1, wherein said permeable sheet comprises a nonwovenfabric cloth or a waterproof converted paper.